Isolate of Antrodia camphorata process for producing a culture of the same and product obtained thereby

ABSTRACT

The present invention relates a process for culturing isolates of  Antrodia camphorata  to provide a product useful in medical and nourishment fields. The present invention also relates to a novel isolate of  Antrodia camphorata  capable of growing in a suitable artificial medium, while exhibiting desired pharmacological activities, in particular anti-tumor activity. The utilization of potato dextrose broth and the synthetic medium containing fructose as major carbon source leads to a significant increase in the pharmacological activity of the cultures of  A. camphorata.

FIELD OF THE INVENTION

The present invention relates a process for culturing isolates ofAntrodia camphorata to provide a product useful in medical andnourishment fields. The present invention also relates to a novelisolate of Antrodia camphorata, the culture of which exhibitspharmacological activities when the isolate is grown in a suitablemedium.

DESCRIPTION OF THE RELATED ART

Antrodia camphorata [(Zang & Su) S.-H. Wu, Ryvarden & T. T. Chang], alsoknown as “niu-chang-chih” or “niu-chang-ku” in Taiwan, was recentlyreported as a new fungus species characterized by the cylindrical shapeof its basidiospores appearing in fruit bodies, weakly amyloid skeletalhyphae, bitter taste and light cinnamon resupinate to pileatebasidiocarps, as well as chlamydospores and anthroconidia in pureculture. The growth of this new fungus species is extremely slow andrestricted to an endemic tree species, Cinnamomum kanehirai Hay(Lauraceae), as the only host. The detailed characterization andtaxonomic position of A. camphorata were described in Chang, T. T. etal., Antrodia cinnamomea sp. nov. on Cinnamomum kanehirai in Taiwan,Mycol. Res. 99(6):756-758 1995) and Wu, S.-H., et al., Antrodiacinnamomea (“niu-chang-chih”), New combination of a medicinal fungus inTaiwan, Bot. Bull. Acad. Sin. 38:273-275 (1997), the entire disclosureof which is incorporated herein by reference.

In Taiwanese folk medicine, the fruit bodies of A. camphorata arebelieved to have certain medical effects. According to the traditionalway, the fruit bodies are ground into dry powder or stewed with otherherbal drugs for oral uptake to treat conditions caused by poisoning,diarrhea, abdominal pain, hypertension, skin itches and liver cancer.However, no pharmacological or clinical study in these aspects hasappeared in literature to date. Because of the stringent hostspecificity and rarity in nature, as well as the failure of artificialcultivation, “niu-chang-chih” is very expensive in Taiwan. In recentyears, the fruit bodies of this fungus with high quality have been soldat an extremely high price of around US $ 15,000 per kg.

Accordingly, there exists a need to establish a method for thelarge-scale cultivation of the fungus A. camphorata in a suitableartificial environment, while maintaining the pharmacological activitiesof the fungus A. camphorata. There also exists a need to obtain anisolate of A. camphorata that exhibits pharmaceutically usefulactivities when cultivated in a suitable artificial environment.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a processsuitable for culturing isolates of A. camphorata, which can grow well inthe mycelial state when subjected to submerged fermentation. For thispurpose, we have tested five isolates of A. camphorata collected in theFood Industry Research and Development Institute (FIRDI), Hsin-Chu,Taiwan, R.O.C. In addition, it is surprising to find that the culture ofan obtained isolate exhibits a desired pharmacological activity, inparticular an anti-tumor activity. According to a preferred embodimentof this invention, the carbon source of the medium, usually acarbohydrate, may be critical to obtain an optimized environment forculturing A. camphorata.

Another object of the present invention is to provide a novel isolate ofAntrodia camphorata bearing a desired pharmacological activity, inparticular an anti-tumor activity, when grown in a suitable artificialenvironment. For this purpose, we have isolated and identified anisolate of A. camphorata, which can grow well in the mycelial state whensubjected to submerged fermentation, and the resulting culture exhibitsexcellent pharmacological activities.

The present invention thus provides a process for producing a culture ofan isolate of A. camphorata having pharmacological activity, comprisingthe steps of:

(a) inoculating a mycelial inoculum of an isolate of A. camphorata intoa medium suitable for the growth of said isolate;

(b) cultivating the resulting culture from step (a); and

(c) harvesting the culture when the culture has a redness index a≧3 asmeasured using Hunter's coordinate system.

A still another object of the present invention is to provide a productobtained from the above process.

A further object of the present invention is to provide a pharmaceuticalcomposition or a nutrient supplement containing a product obtained fromthe above process.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent with reference to the following description of thepreferred embodiments taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram demonstrating the growth of tumor cells affected bythe culture filtrate derived from a shake culture of A. camphorata CCRC930032 in potato dextrose broth, in which the tested cell lines includeHela, ES-2, Hep 3B, MCF-7, AGS, COLO 205, COLO 320HSR, and Caco-2;

FIG. 2 is a diagram demonstrating the growth of tumor cells affected bythe culture filtrates derived from shake cultures of A. camphorata CCRC930032 in synthetic media, in which the tested cell lines include Hela,AGS, COLO 320HSR, Hep G2 and MCF-7 cells;

FIG. 3 is a diagram demonstrating the inhibiting effect of the shakeculture filtrates of A. camphorata CCRC 930032 harvested at differentsampling time points on the growth of tumor cells, in which the testedcell lines include Hela, AGS, Hep 3B2.1-7, and MCF-7 cells;

FIG. 4 is a diagram demonstrating the growth of tumor cells affected byfive-, ten- and twenty-fold diluted culture filtrates of A. camphorataCCRC 930032, in which the tested cell lines include Hela, ES-2, Hep 3B,MCF-7, AGS, COLO 205, COLO 320HSR, and Caco-2 cells; and

FIG. 5 is a diagram demonstrating the growth of tumor cells affected bythe shake culture filtrates derived from five isolates of A. camphorata,i.e. CCRC 35396, 35398, 36401, 36795 and CCRC 36799, in which the testedcell lines include ES-2, AGS, Hep 3B2.1-7, and MCF-7 cells.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, one isolate of A. camphoratawas isolated from Taitung County, Taiwan, R.O.C., and this and otherfour isolates of A. camphorata were successfully cultivated in a naturalsource medium or a synthetic medium. These five isolates were depositedin the Culture Collection and Research Center (CCRC) of the FoodIndustry Research and Development Institute (FIRDI), Hsinchu, Taiwan,R.O.C. under accession numbers CCRC 35396 (on Dec. 1, 1994), 35398 (onDec. 1, 1994), 36401, 36795 and 930032 (on Jan. 27, 2000), respectively.

The term “natural medium” as used herein takes on its common meaning toa person skilled in the art and is directed to a medium mainlyconsisting of naturally occurring materials. According to the presentinvention, the commercially available potato dextrose broth from GIBCOis preferred.

The term “synthetic medium” as used herein is directed to an artificialmixture of various ingredients with defined chemical structures andoptionally one or more crude ingredients derived from natural materials.In general, a synthetic medium comprises a carbon source, a nitrogensource, trace elements such as an inorganic salt, and optionallyvitamins or other growth factors.

The carbon source includes but is not limited to glucose, sucrose,galactose, fructose, corn starch, malt extract and combinations thereof.From the view point of the intended effects, the synthetic mediumpreferably contains fructose as a major carbon source, and optionallysupplemented with malt extract or glucose. Preferably, the carbon sourceis present in the range between 1.5-2.5% by weight, and more preferablyin an amount of 2.5% by weight, on the basis of the total volume of thesynthetic medium.

The nitrogen source includes but is not limited to ammonium sulfate,ammonium nitrate, sodium nitrate, casamino acid, yeast extract, peptone,tryptone and combinations thereof. Preferably, according to the presentinvention, the synthetic medium contains yeast extract as the nitrogensource. The nitrogen source is preferably present in the range between0.2-2.0% by weight, and more preferably in an amount of 0.5% by weight,on the basis of the total volume of the synthetic medium.

The process of the present invention apparently has advantages of easymanipulation and ready access to the large-scale production of thedesired fungus in the pharmaceutics industry, as compared with thetraditional method of manipulating “niu-chang-chih,” such as groundingand stewing the fruit bodies of the fungus per se.

The five isolates of A. camphorata were tested for their potential inthe medical field, in particular their ability to inhibit the growth oftumor or cancer cells. To evaluate the competence of these isolates ininhibiting the growth of tumor cells, the aqueous phases of A.camphorata cultures in the natural and synthetic media were subjected toan MTT colorimetric assay.

The term “MTT colorimetric assay” or “MTT-tetrazolium assay” as usedherein is directed to an anticancer drug screening scheme established inthe 1980s by the U.S. National Cancer Institute's DevelopmentalTherapeutics Program, Division of Cancer Treatment (see, for example,Alley, M. C., et al., Feasibility of drug screening with panels of humantumor cell lines using a microculture tetrazolium assay Cancer Res.48:589-601, 1988; Scudiero, D. A., et al., Evaluation of a solubletetrazolium/formazan assay for cell growth and drug sensitivity inculture using human and other tumor cell lines. Cancer Res.48:4827-4833, 1988; Vistica, D. T., et al., Tetrazolium-based assays forcellular viability: a critical examination of selected parametersaffecting formazan. Cancer Res. 51:2515-2520, 1991; and Monks, A., etal., Feasibility of a high-flux anticancer drug screen using a diversepanel of cultured human tumor cell lines. J. Nat. Cancer Inst.83:757-766, 1991).

In the assay, potential anticancer drugs or natural products derivedfrom plants or microbes (in this case, from the five isolates of A.camphorata ) were tested for their ability against groups of cell linepanels each representing a major clinical category of human malignancy.The viable cell numbers per well are directly proportional to theproduction of formazan, which can be measured spectrophotometricallythrough solubilization. In principle, biologically active substances ornatural products containing the substances can inhibit or even stop cellgrowth, and little formazan is formed consequently.

Amongst the five isolates, A. camphorata CCRC 930032, also deposited atthe American Type Culture Center (ATCC) with accession no. PTA-1233 onJan. 27, 2000 under the terms of the Budapest Treaty on theInternational Recognition of the Deposit of Microorganism for thePurpose of Patent Procedure, is found to have excellent pharmacologicalactivity. In particular, the results from the MTT calorimetric assayreveal that A. camphorata CCRC 930032 when grown in the designed cultureconditions (in potato dextrose broth or the synthetic medium containingfructose as the major carbon source) possesses excellent anti-tumoractivities.

In view of our success of cultivating A. camphorata CCRC 930032 usingthe selected media, it will be appreciated by those skilled in the artthat new isolates of A. camphorata having pharmacological activitycharacteristics substantially identical to those of A. camphorata CCRC930032 can be isolated and cultivated using the present method describedabove.

Presumably, the unknown active substance(s) functioning to the targettumor cells are produced and secreted from the mycelium into the liquidphase of the culture if a suitable environment, such as the specificcompositions in the medium, is given. Accordingly, our unexpectedfinding suggests a feasible process for large-scale production of A.camphorata by the optimized scale-up fermentation and a utilization ofthe cultures derived therefrom to manufacture useful materials, such ashealthy food.

The present invention is therefore beneficial to the susceptibility ofA. camphorata to herbal medicine applications. The present inventionalso opens a gate to utilization of the obtained A. camphorata culturein the treatment of cancer or tumor diseases in a patient in need ofsuch treatment.

Preferred Embodiments for Practicing the Invention

The following Examples are given for the purpose of illustration onlyand are not intended to limit the scope of the present invention.

EXAMPLE 1 Preparation of Liquid Cultures of A. camphorata CCRC 930032 inNatural Media

Maintenance of Culture

The stock culture A. camphorata isolate CCRC 930032, which is depositedin the Culture Collection and Research Center (CCRC), was maintainedwith slant tubes of potato dextrose agar (PDA, purchased from Difco) at25° C. and sub-cultured every two months. Working cultures on PDA plateswere inoculated from PDA slants and incubated at 28° C. from 15 to 20days.

Preparation of Mycelial Inoculum

After an incubation period from 15 to 20 days, the mycelialcharacteristics of Antrodia camphorata CCRC 930032 were investigatedunder a light microscope to assure that no contamination occurred. Thewhole mycelia was cut into small pieces and then homogenized asepticallywith 50 ml of sterile water in a homogenizer (Osterizer) for 30 seconds.10 ml aliquots of the mycelial suspension were used as inoculum for thesubsequent experiment.

Submerged Shake Culture

Potato dextrose broth (PDB, purchased from Difco) was prepared accordingto the instructions provided by the manufacturer. To 100 ml of thenatural source medium in 500 ml Erlenmeyer flasks, 10 ml inoculum of A.camphorata CCRC 930032 was added. The submerged cultures were incubatedat 30° C. for 14 days with constant agitation (at 50 rpm on an orbitalrotary shaker purchased from Hotech). At the end of incubation, thefungus cultures were passed through a simple filtration assembly of asuction filter funnel, a flask and a vacuum machine. The filtrates wereused for the subsequent MTT calorimetric assay. The pellets harvested onthe funnel were baked at 60° C. for 7 days, and the dry weights of thetotal cell mass were calculated. The experiment was triplicated.

EXAMPLE 2 Preparation of Liquid Cultures of A. camphorata CCRC 930032 inSynthetic Media

Example 1 was repeated except that the natural medium was replaced withsynthetic media, each containing 0.5% (w/v) of yeast extract (Difco),0.1% (w/v) of KH₂PO₄ (Merck), 0.05% (w/v) of MgSO₄. 7H₂O (Merck) and2.5% of a selected carbohydrate, i.e., fructose, glucose, sucrose, maltextract or corn starch, as the major carbon source. The experiment wasalso triplicated.

The results of Examples 1 and 2 are shown in Table 1.

TABLE 1 Dry weight of mycelium of A. camphorata CCRC 930032 grown indifferent culture media (fixed culture condition: 30° C., 50 rpm, andincubation for 14 days.) Dry weight of Culture medium mycelium (g/L)Color of broth Potato dextrose broth: 2.4 grams suspended in 100 ml2.776 deep dark red distilled water Synthetic medium: 0.5% yeast extract(Difco), 0.1% KH₂PO₄ (Merck), and 0.05% MgSO₄.7H₂O (Merck) matched with2.5% of different carbon sources: (1) fructose 3.526 dark red (2)glucose 3.661 yellow (3) malt extract 5.02 brown (4) corn starch 5.384pale yellow

As shown in Table 1, the mycelia of the highest dry weights wereobtained in the synthetic media with corn starch or malt extract as acarbon source. The average sizes of the mycelial pellets were fairlysmall, usually about 1-3 mm in diameter. The colors of the resultantcultures were variable and seem to depend upon the compositions includedtherein. For instance, the cultures obtained from potato dextrose brothappeared deep dark red in color, and a similar color was observed in thecultures derived from the synthetic medium added with fructose as themajor carbon source. On the other hand, the colors shown in the rest ofthe cultures look quite different. The cultures resulting from thesynthetic medium with glucose or corn starch as a carbon source turnedyellow at the end of incubation, whereas the color of the culturesoriginating from the synthetic medium with malt extract was brown.

EXAMPLE 3 MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazoliumbromide) Colorimetric Assay

Preparation of Samples for MTT Assay

The culture filtrates of A. camphorata collected in Examples 1 and 2(experimental samples) and the non-inoculated media (control samples)were used for MTT assay. The culture filtrates and media were adjustedwith NH₄OH to pH 7 and sterilized by autoclaving. The resultant sampleswere preserved at 4° C. before analysis.

Cell Lines and Culture

Tumor cell lines, including MCF-7, Hela, AGS, COLO 320HSR, and Hep G2cells, etc., were selected for MTT calorimetric assay. They weremaintained as stocks in RPMI 1640 (GIBCO BRL) supplemented with 10%fetal bovine serum (Hyclone) and 2 mM L-glutamate (GIBCO BRL). Thecultures of these cell lines were passaged once or twice weekly usingtrypsin-EDTA (GIBCO BRL) to detach the cells from cell culture flasks.

MTT-microculture Tetrazolium Assay

Tumor cells were harvested, counted and inoculated into a 96-wellmicrotiter plate at the appropriate concentrations. For example, thestart-up concentration of Hela cells was 1000 cells per well, and thoseof Hep3B2.1-7, HepG2, AGS, COLO 320HSR and MCF-7 cells were 3000 cellsper well. The total volume of the cell culture medium in each well wasmade up to 180 μl, and an incubation was carried out overnight at 37° C.in an incubator containing 5% CO₂.

20 μl aliquots of the samples were applied to the culture wells intriplicate, and the resultant cultures were incubated for 3 days in theabove-mentioned incubation condition. Subsequently, 20 μl of MTT(Merck), prepared previously at 5 mg/ml in PBS solution (GIBCO BRL) andstored at 4° C., were added to each well.

After an additional 4-hour incubation at 37° C., the supernatant wasremoved from each well, and 100μl of 100% DMSO (dimethyl sulfoxide,available from Sigma) were added, in order to solubilize theMTT-formazan product. After thorough mixing with a mechanical platemixer, absorbance at 540 nm was measured with a microplate reader (MRX,Dynex). The tumor cell growth inhibition rates of the tested culturefiltrates of A. camphorata were calculated by dividing the absorbance ofeach experimental sample by that of the corresponding control sample.The results are shown in FIGS. 1 and 2.

In FIG. 1, the selected culture medium is potato dextrose broth, and theincubation of A. camphorata isolate CCRC 930032 was conducted at 30° C.,50rpm, 10% inoculation volume for 14 days (Example 1). A culturefiltrate was harvested from the culture and was incubated and tested inan MTT-tetrazolium assay against several typical tumor cell lines,including Hela, ES2, Hep3B, MCF-7, AGS, COLO 205, COLO 320HSR and Caco-2cells.

FIG. 1 shows that the growth rates of the tumor cell lines areremarkably reduced by the addition of the culture filtrate from A.camphorata isolate CCRC 930032 in potato dextrose broth, as compared tothe results from the control samples. For instance, the MCF-7 cellstreated with the culture filtrate of Example 1 has a growth rate of 8%based on the growth rate of its counterpart control, whereas the COLO320HSR and AGS cells so treated have a growth rate of only 4%.

In FIG. 2, the synthetic medium composition as listed in Table 1 wereemployed, and the incubation lasted for 14 days at 30° C., 50rpm, 10%inoculation volume. Five tumor cell lines, including Hela, MCF-7, AGS,COLO 320HSR and MCF-7 cells, were used for the MTT-tetrazolium assay. Asshown in FIG. 2, a significant inhibitory effect on the growth of thetumor cells was observed in the cells treated with the culture filtratesfrom the synthetic media having fructose as the major carbon source. Inaddition, the growth rates were reduced to below 20% in COLO 320HSR andMCF-7 cell lines. Surprisingly, A. camphorata isolate CCRC 930032 doesnot significantly inhibit the growth of the tumor cell lines whencultured in the same synthetic medium having glucose, malt extract andcorn starch as the major carbon source, respectively. Moreover, theinhibitory ability of A. camphorata isolate CCRC 930032 was reduceddramatically and was restricted to AGS and MCF-7 tumor cell lines whenthe culture medium, for certain reasons, sometimes fails to show a darkred color.

Accordingly, the dark red appearance of the culture filtrates from thepotato dextrose broth and the synthetic medium containing fructosesuggests that the observed inhibitory effects of the tested funguscultures on the tumor cells are possibly correlated with the color ofthe culture. This presumption is further investigated in Example 4.

EXAMPLE 4 Coincidence of the Inhibitory Activity and Color Appearance ofA. camphorata Filtrates

In this example, the isolate CCRC 930032 was cultured in a 5-literfermenter. Samples were removed from the culture at the 143rd, 167th,216th, 239th, 263rd, 287th and 311st hours after the inoculation andwere used for MTT-tetrazolium assay. The collected culture samples weredetected with a Lovibond Tintometer PFX990, and the color appearances ofthe samples are represented by the “L,” “a” and “b” coordinates inHunter's coordinate system, in which a larger “L” value refers to ahigher level of brightness, a more positive “a” value refers to a higherlevel of redness and a more positive “b” value refers to a higher levelof yellowness. The start-up medium was used as a blank standard. Theresults are shown in FIG. 3 and Table 2 below.

TABLE 2 The tintometric analysis of the filtrate samples of A.camphorata CCRC 930032 picked up at the 143rd, 167th, 216th, 239th,263rd, 287th and 311st hours after the mycelial inoculation. SamplingTime (hour) L a b 143 63.12 3.71 18.03 167 79.09 4.04 20.56 216 76.048.62 25.60 239 76.50 10.67 24.34 163 75.34 12.91 27.30 187 74.47 13.9429.74 311 73.26 14.94 33.42

It can seen that the growth rates of the tumor cells drop significantlyas the “a” values (i.e., the redness) of the filtrates increaseabruptly. While a 20% inhibition against the tested tumor cells is shownwhen the “a” value of the culture filtrate is above 3, it is estimatedby interpolation that the desired filtrates, i.e., the filtrates with ahigher inhibitory effect on tumor cells, have an “a” value above 7 wherethe redness can be observed with bare eyes.

Without wishing to be limited by theory, it is presumed that the isolateCCRC 30032 may have an advantageous genetic background and thereforecomprises, for example, a set of enzymes, which facilitate theproduction and/or the secretion of the active substance(s) in particularculture media. The metabolites, together with the environment of themedium, result in the color change of cultures from yellow to dark red.Perhaps, the active substances per se contain conjugated double bonds,such as terpenoids, and thus impart a dark red color to the liquidcultures to which they are secreted. Accordingly, the color appearanceof the cultures may be a useful indicator for assessing the inhibitoryactivity of the culture.

EXAMPLE 5 The Inhibitory Effect on the Growth of Tumor Cells by theDiluted Culture Filtrates

To identify the inhibitory strength of A. camphorata isolate CCRC 930032against the growth of the tumor cells, the culture filtrate producedfrom a culture of the microorganism in potato dextrose broth was dilutedin five-, ten- and fifty-fold and was subjected to the MTT-tetrazoliumassay. The result illustrated in FIG. 4 demonstrates that as thedilution fold increases, the inhibitory effect of the culture filtrateon the tumor cells decreases gradually in a dosage-dependent manner.Nevertheless, significant inhibition to the growth of Hep 3B, AGS, ES-2,and COLO 320HSR cell lines was observed by using the five-fold dilutedfiltrate. The growth rate of the ES-2 and COLO 320HSR cells treated bythe 50-fold diluted filtrate were still inhibited to below fortypercent, as compared to the results from the non-treated cells.

EXAMPLE 6 Inhibitory Effects of the Cultures of Different Isolates of A.camphorata Upon Tumor Cells

Examples 1 and 3 were repeated except that the A. camphorata isolateCCRC 930032 was replaced with four other isolates, CCRC 35396, 35398,36401 and 36795, respectively. At the end of incubation, the filtratesderived from the four isolates all appear yellow in color. Asillustrated in FIG. 5, the results reveal that isolate CCRC 930032 issuperior to the other four isolates in terms of the activity ininhibiting the growth of the tested tumor cells. A. camphorata isolateCCRC 930032 thus appears to be a promising candidate for the manufactureof a pharmaceutical composition or a nutrient supplement.

While the invention has been described with reference to the abovespecific embodiments, it should be recognized that various modificationsand changes which will be apparent to those skilled in the relevant art,may be made without departing from the spirit and scope of theinvention.

We claim:
 1. An isolate of Antrodia camphorata, wherein the isolate,when cultured in a medium selected from potato dextrose broth or asynthetic medium containing fructose as a major carbon source, resultsin a color appearance of the culture that has a redness index a≧3 asmeasured using Hunter's coordinate system; and the isolate is depositedin the Food Industry Research and Development Institute (FIRDI) with anaccession number CCRC 930032 and in the American Type Culture Center(ATCC) with an accession number PTA-1233.